Turbine engines are used as the primary power source for various kinds of aircraft. The engines may also serve as auxiliary power sources that drive air compressors, hydraulic pumps, and industrial electrical power generators. Most turbine engines generally follow the same basic power generation procedure. Compressed air is mixed with fuel and burned, and the expanding hot combustion gases are directed against stationary turbine vanes in the engine. The vanes turn the high velocity gas flow partially sideways to impinge onto turbine blades mounted on a rotatable turbine disk. The force of the impinging gas causes the turbine disk to spin at high speed. Jet propulsion engines use the power created by the rotating turbine disk to draw more air into the engine, and the high velocity combustion gas is passed out of the gas turbine aft end to create forward thrust. Other engines use this power to turn one or more propellers, electrical generators, or other devices.
Because fuel efficiency increases as engine operating temperatures increase, turbine engine blades and vanes are typically fabricated from high-temperature materials such as nickel-based superalloys. However, although nickel-based superalloys have good high temperature properties and many other advantages, they may be susceptible to corrosion, oxidation, thermal fatigue, and foreign particle impact in the high temperature environment during turbine engine operation. In such cases, the turbine engine blades and vanes may need to be repaired, such as, by welding, by a diffusion brazing process or by a combination of both welding and diffusion brazing.
Diffusion brazing processes typically employ a braze alloy mixture that includes a base alloy material (also referred to as a “high-melt alloy”) and a braze alloy material (also referred to as “a low-melt alloy”). The high-melt alloy is usually a material that is substantially similar in composition to the material of the component being repaired, while the low-melt alloy typically comprises a braze alloy powder including a relatively low volume fraction (e.g., less than 50%) of gamma prime and small amount of solid solution strengthening alloying elements and has a melting temperature that is lower than that of the high-melt alloy. After a slurry coating of the braze alloy mixture is applied to a repair area on the turbine component and subjected to heat treatment in a vacuum furnace, the mixture melts and heals cracks and builds up material loss on the repair area. Although the aforementioned processes are suitable for performing certain repairs, they may not be useful for others.
Hence, it is desirable to have an improved process for repairing turbine engine components such as the turbine engine nozzles and vane segments. It is also desirable for the repair process to be cost-effective. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.